1. Field of the Invention
The invention relates to a method for hydrogenating benzyl compounds, particularly acetophenone, in the presence of a Ru catalyst, to form the corresponding cyclohexyl compounds.
2. Discussion of the Background
The general object of the inventive method is to produce cyclohexyl compounds in a simple and economical procedure, with high purity and high yield.
1-Cyclohexyl-1-ethanol is of interest as a starting substance for producing vinylcyclohexane which is employed in polymer chemistry.
Hydrogenation of benzyl compounds to the corresponding saturated cyclohexyl compounds with the aid of Ru, Rh, and Pd catalysts is known, but the known methods are characterized by low yields, particularly due to the formation of cycloparaffins.
The principal means of eliminating these drawbacks has been the use of catalyst combinations, as described in USSR Pat. No. 733,710 (Ru+Cr, on alumina), USSR Pat. No. 405,323 (Rh+Ru, on alumina), USSR Pat. No. 448,703 (Ni+Cr), and Tetrahedron Letters, 17, 1663-1664 (1977) (Pd, Pd+Rh, Pd+Ru, on carbon); or by the addition of alkali, for example, as described in U.S. Pat. No. 3,366,695. The addition of acids is also known. These techniques do in fact lead to improved yields, but they require additional process steps.
According to Zh. Prikl. Khim., 42(11), 2613-1614 (1969), Rh catalysts should be particularly suitable. Pd catalysts are relatively ineffective, particularly at higher pressures.